Office of Water (4607M) 815–F-09-002 March 2010 

www.epa.gov/safewater 

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Fact Sheet: Announcement of 

Completion of EPA's Second Review of 

Existing Drinking Water Standards 

The Safe Drinking Water Act (SDWA) requires EPA to review each National Primary Drinking 

Water Regulation (NPDWR) at least once every six years and revise them, if appropriate. The 

purpose of the review, called the Six-Year Review, is to identify those NPDWRs for which current 

health effects assessments, changes in technology, and/or other factors provide a health or technical 

basis to support a regulatory revision that will maintain or strengthen public health protection.

Questions and Answers 

1. What is the Environmental Protection Agency (EPA) announcing? 

In March 2010, the Agency announced the completion of its second review of existing 

NPDWRs (i.e., the Six-Year Review 2). After performing a detailed review of 71 existing 

NPDWRs, the Agency determined that 67 NPDWRs remain appropriate (i.e., do not need to be 

revised) and 4 NPDWRs are candidates for regulatory revision. These four NPDWRs include 

acrylamide, epichlorohydrin, tetrachloroethylene, and trichloroethylene. In addition to the 71 

NPDWRs, this review includes 14 other NPDWRs that did not need a detailed review because of 

recent or ongoing regulatory actions.

2. Why did EPA review these NPDWRs? 

The 1996 SDWA Amendments require EPA to periodically review existing NPDWRs and, if 

appropriate, revise them. This requirement is contained in Section 1412(b)(9) of SDWA, which 

reads: 

The Administrator shall, not less often than every 6 years, review and revise, as appropriate, 

each national primary drinking water regulation promulgated under this title. Any revision 

of a national primary drinking water regulation shall be promulgated in accordance with 

this section, except that each revision shall maintain, or provide for greater, protection of 

the health of persons. 

3. What NPDWRs are covered by this action? 

The Six-Year Review process only applies to existing national primary drinking water regulations 

(i.e., currently regulated contaminants). Unregulated contaminants, such as those listed on the 

Contaminant Candidate List (CCL) are not covered by the Six-Year Review. The current 2003-

2009 review specifically focused on a detailed review of 71 NPDWRs promulgated prior to 2005. 

The Agency included 14 other NPDWRs (e.g., lead, copper, disinfection byproducts, and the 

microbiological NPDWRs) in the review. However, these regulations did not need a detailed 

assessment because they are the subject of recent or ongoing rulemaking activity. 
Office of Water (4607M) 815–F-09-002 March 2010 

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4. How did EPA review the NPDWRs? 

The primary goal of the Six-Year Review is to identify, prioritize and target candidates for 

regulatory revision that are most likely to result in a meaningful opportunity for health risk 

reduction and/or cost savings to public water systems and their customers while maintaining or 

providing for greater levels of public health protection. To address this goal and as part of the 

first Six-Year Review (i.e., Six-Year Review 1), EPA developed a protocol to perform the review 

based on extensive inputs that included consultations with the National Drinking Water Advisory 

Council (NDWAC) and the Science Advisory Board. For Six-Year Review 2, EPA applied the 

same protocol with some refinements to improve the tracking of a contaminant through the 

decision process. 

The protocol focuses on several key elements that are intended to identify NPDWRs for which 

there is a health or technological basis for revising the NPDWR. The review relied upon an 

evaluation of relevant, new information for the following key technical elements: health effects, 

analytical methods improvements, treatment technology effectiveness, occurrence and exposure 

analyses, and other potential regulatory changes. Figure 1 provides a general overview of the 

protocol used to evaluate the NPDWRs and categorize the results (i.e., revise/take no action). 

Figure 1. Six-Year Review Protocol Overview and Major Categories of Revise/Take No Action Outcomes.

Yes

No

New information to suggest possible changes (i.e., 

to an MCLG, MCL, Treatment Technique and/or 

other regulatory revisions)?

Meaningful opportunity for health risk reduction for 

persons served by PWS and/or cost savings while 

maintaining/improving public health protection?

Outcome:

No action 

at this time

Outcome:

Candidate 

for Revision

Data sufficient to support

regulatory revision?

No new information

Low priority - No meaningful 

opportunity

Data gaps/emerging 

information

Yes

No

Ongoing or planned HEA

Health effects assessment (HEA)

in process or planned? *

NPDWRs Under Review

Yes

No

Yes

No

NPDWR reviewed in recent or ongoing action? 

No

Yes Regulatory action ongoing

or recently completed

* Contaminants with an HEA in process that have an MCL based on practical quantitation

limit and are greater than MCLG are passed to the next question to evaluate potential to 

revise the MCL. If EPA found that there were no changes in technology (i.e., analytical 

feasibility or TT) or if changes were possible but there was no meaningful opportunity to 

revise the MCL or TT, these contaminants remained in the ongoing health effects category.

Uncertain – emerging

information
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5. What are the overall review results for Six-Year Review 2? 

Based on its review, EPA believes that four NPDWRs are candidates for regulatory revision. These 

four NPDWRs are acrylamide, epichlorohydrin, tetrachloroethylene, and trichloroethylene. EPA 

believes the remaining 67 NPDWRs are not appropriate for revision due to one or more of the 

following reasons: 

• A health effects assessment is in process or the Agency is considering whether to initiate 

an assessment; 

• The NPDWR remains appropriate after review of new, relevant data/information; 

• New, relevant information is available that indicate a potential change in the NPDWR 

but no revision is recommended because it would result in a negligible gain in public 

health protection and/or cost savings; or 

• Information gap(s) and/or emerging information were identified. 

Table 1 lists EPA’s review results for each of the 71 NPDWRs that were a part of this detailed 

review along with the principal rationale for the review outcomes. Table 1 also includes a list of the 

14 NPDWRs that have been or are being reviewed/revised by recent or ongoing regulatory actions.. 

6. Will EPA consider reviewing any NPDWRs before the next review cycle? 

If the result of any ongoing health risk assessment or the resolution of data gaps/research needs 

indicate that significant or compelling new information becomes available that will change the basis 

for an NPDWR, the Agency may decide to accelerate the review schedule for a particular NPDWR. 

7. What are the next steps? 

EPA will consider the public comments and/or any new, relevant, peer-reviewed data submitted for 

the four NPDWRs listed as candidates for revision as the Agency proceeds with the regulatory 

revisions for these regulations. The announcement that the Agency intends to revise an NPDWR 

(pursuant to SDWA section 1412(b)(9)) is not a regulatory decision. Instead, it initiates a 

regulatory process that will involve more detailed analyses of health effects, analytical and 

treatment feasibility, occurrence, benefits, costs, and other regulatory matters relevant to deciding 

whether an NPDWR should be revised. The Six-Year Review results do not obligate the Agency to 

revise an NPDWR in the event that EPA determines during the regulatory process that revisions are 

no longer appropriate and discontinues further efforts to revise an NPDWR. Similarly, the fact that 

an NPDWR has not been selected for revision means only that EPA believes that regulatory 

changes to a particular NPDWR are not appropriate at this time for the reasons listed in the answer 

to question 5. 

8. Where can I find more information about this notice and the Six-Year Review? 

For information on the Six-Year Review, please visit the EPA internet website, 

www.epa.gov/safewater/review.html. For general information on drinking water, please visit the 

EPA Safewater website at www.epa.gov/safewater or contact the Safe Drinking Water Hotline at 1-
Office of Water (4607M) 815–F-09-002 March 2010 

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800-426-4791. Local or international calls can reach the Hotline at 703-412-3330. The Safe 

Drinking Water Hotline is open Monday through Friday, excluding legal holidays, from 10:00 a.m. 

to 4:00 p.m. Eastern time.
Office of Water (4607M) 815–F-09-002 March 2010 

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Table 1. Summary of Six-Year Review 2 Results

Recent or Concurrent Action 

(14 NPDWRs) 

Bromate 

Chloramines 

Chlorine 

Chlorine dioxide 

Chlorite 

Coliform 

Copper 

Cryptosporidium 

Giardia lamblia 

HAA5 

Lead 

Legionella 

TTHMs 

Viruses 

Health effects assessment in 

process or potential nominee for an 

assessment 

(32 NPDWRs) 

Alpha particles (or emitters)1

Antimony 

Arsenic 

Asbestos 

Benzo(a)pyrene1

Beryllium 

Beta particles and photon emitters1

Cadmium 

Carbon tetrachloride1

Chromium 

Cyanide 

1,2-Dichlorobenzene 

1,4-Dichlorobenzene 

1,2-Dichloroethane1

cis-1,2-Dichloroethylene 

trans-1,2-Dichloroethylene 

Dichloromethane1

Di(2-ethylhexyl)adipate1

Di(2-ethylhexyl)phthalate1

Ethylbenzene 

Fluoride 

Nitrate 

Nitrite 

Pentachlorophenol1

Polychlorinated biphenyls (PCBs)1

Radiums1

Selenium 

Styrene 

2,3,7,8-TCDD (dioxin)1

Thallium 

1,2,4-Trichlorobenzene 

Uranium 

NPDWR remains appropriate after 

data/information review 

(8 NPDWRs) 

Dalapon 

Dinoseb 

Endrin 

Ethylene Dibromide (EDB) 

Mercury (inorganic) 

Methoxychlor Monochlorobenzene 

(chlorobenzene) 

2,4,5-Trichorophenoxy-propionic acid 

(2,4,5-TP) 

Low priority 

(24 NPDWRs) 

Alachlor 

Barium 

Benzene 

Chlordane 

1,2-Dibromo-3-chloropropane 

(DBCP) 

1,1-Dichloroethylene 

1,2-Dichloropropane 

2,4-Dichlorophenoxyacetic acid (2,4-

D) 

Diquat 

Endothall 

Glyphosate 

Heptachlor 

Heptachlor epoxide 

Hexachlorobenzene 

Hexachlorocyclopentadiene 

Lindane 

Oxamyl 

Picloram 

Toluene 

Toxaphene 

1,1,1-Trichloroethane 

1,1,2-Trichloroethane 

Xylenes 

Vinyl chloride 

Not Appropriate 

for Revision at 

this Time 

New 

information, 

but no 

revision 

recommended 

because: 

Emerging information

or data gaps 

(3 NPDWRs) 

Atrazine 

Carbofuran Simazine 

Candidate 

for Revision 

Based on new information 

(4 NPDWRs) 

Acrylamide2

Epichlorohydrin 

Tetrachloroethylene (PCE)2

Trichloroethylene (TCE)2

1. For these compounds, there is no potential to change the MCL based on changes in analytical feasibility or there may be a 

potential change to the MCL based on analytical feasibility but any such change is unlikely to provide a meaningful opportunity to 

improve public health protection. Therefore, EPA chose to leave these in the ongoing health assessment category. 

2. Note that a health assessment is in process but new analytical feasibility and TT information may justify a revision